How do i select perennial plants, sun n shade, self-spreaders??
by
Shuganne
In other words, there's just no room for my lawn tractor to mow in front of my house. I would love aggressive varieties to choke out the typical grass and weeds. I'm not sure what zone I'm in, but I live in northern Illinois. I have lots of trees but still about 2 acres of pure sun. I'd be fine with a couple varieties and let them select where they'd like to thrive. I need them to be natural spreaders and I'm in the country, so I'm happy with wildflowers and native species. Also inexpensive. 
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Creeping thyme and phlox are two I thought of.
First, talk to your neighbors about plants that grow easily. If you see someone working in their garden, even if you don't know them, stop and ask them about their plants. Most gardeners like to talk about their gardens. You may get free plants just by asking gardeners where they got theirs. In my area we can transplant many bulbs and perennials at the end of August and through September. Visit a local nursery (not Home Depot or Walmart) and ask them which plants they recommend for your needs.
Plant white clover, it will eventually choke out other weeds, you never have to mow if you do not want to and is nice and fluffy and fun to roll around in.
Here is how to find your zone:
http://planthardiness.ars.usda.gov/PHZMWeb/